[NetworkSuggestion] Allow app to set subId for the suggestion

SubId will be used to identify which SIM/subscription to use for this
suggestion. Same network with different SubIds will be consider
different suggestions.
Also add a system API in WifiConfiguration to help data calculation for
different SIM.

Bug: 169275787
Test: atest android.net.wifi

Change-Id: I093c0661e28cc2df5e97391342101e8ecc331a0f